The Japanese sea lion is an eared seal which is thought to have become extinct in the 1970s. It inhabited the Sea of Japan and was perhaps one of the largest sea lions in the world.
Taxonomy and extinction
This species, known by its scientific name Zalophus japonicus, belongs to the Zalophus genus alongside the California sea lion and the Galapagos sea lion. It was included in the subfamily Otariinae and the family Otariidae alongside fur seals. Until 2003, the Japanese sea lion was considered a subspecies of the California sea lion. Further studies, as well as the differences in habitat and behavior, have prompted scientists to name Zalophus japonicas a distinct species. By 1915, there were only 300 specimens left, and in 1974, the last juvenile specimen from Rebun Island died.
This species closely resembled the California sea lion, which still exists today. Males were larger than females and presented a mane as well as a sagittal crest
which gave them a bumped forehead appearance. Males reached 2.5 meters in length and could weigh between 450 and 560 kg. Females could grow to 1.64 meters in length. The bodies of the males were stockier, with broader necks, chests and shoulders than females which had a wider abdomen. Males were darker in color than females and pups, which were lighter and orange.
Habitat of the Japanese sea lion
These sea lions inhabited the offshores and islands of the Sea of Japan. Populations were also found on the coast of the Korean Peninsula and could extend up north to the southern tip of the Kamchatka Peninsula. There are also some old Korean accounts which describe these seals to have inhabited the Bohai Sea and the Yellow Sea. Populations could be found breeding on sandy beaches, but were also present on gravel or pebble beaches and rarely on rock groups. A distinct characteristic of this species is that, opposite to other sea lions that rested on the same grounds where they bred, they preferred to rest inside caves.
Little is known about the reproduction habits of these sea lions. Given the morphological similarities between the Japanese and California sea lions and the size of adult males of the former, it is reasonable to suspect that bulls fought for territories and tried to maintain control of as many females as possible. Japanese sea lion pups were most likely intensely looked after for a few weeks and weaned after a year.